Check here for a succinct presentation of relatively current relevant info in RE your request:
http://www.elnexus.com/articles/Opteron-Xeon-Benchmarks-2012-01.aspx
For me, a 2P (or better, 4P) Opteron solution makes the most sense; for a mobo, Asus is probably the low-price champ in the 2P arena; Supermicro (aka: A+) 2P and 4P boards are about twice what you'd expect to pay for a decent consumer board socketed for a single Sandy Bridge cpu.
Most boards for the 6200-series Opterons can use common, relatively inexpensive, unbuffered consumer-grade RAM; if you're worried about baking your memory in a 24/7/365 solution, Koolance offers a liquid-cooling kit for such RAM (and also has water blocks for the G34 and C32 Opterons).
The motherboards for the Opteron are almost entirely geared towards server applications; however, some Opteron workstation solutions are on the market using a 2P Supermicro mobo.
As to why an Opteron workstation might use a mobo made and marketed for servers, at this level, I don't think it's reasonable to simply dismiss such a choice as a concession to expedience:
My guess is that performance for at least most workstation applications using the AMD CPU is sufficiently great, and that optimization of the board for workstation performance would yield such small improvement that such optimization would not be a worthwhile deployment of the mobo-manufacturer's resources -- a fact somewhat aggravated both by consumer prejudice and by AMD's election to market the Opterons as "server" CPUs.
If cost is an issue, consider the socket C32 Opterons: Asus and Tyan have 2P motherboards for these CPUs; I can't recall right now, but there is at least one ATX mobo for dual socket-C32 Opterons; a 2P server/workstation build using 4200-series Opterons would be cost-competitive with a 1P consumer-grade Core i7-2600K machine and would offer performance much improved over the Intel product.
Some people would say that isn't a fair contrast: the i7 mobo is usually available with particular cutting-edge tech not present on a server mobo (favors the i7 if you need an interface not supported on the server board) or the 4200-series Opteron is a low-end server CPU being compared to a mid-range consumer CPU (favors the Opteron, especially where cost is important and "mainstream tech" provides adequate connectivity and real-world performance).
I don't perceive any disadvantage in RE complexity of construction or operation as differentiating the 2P Opteron solution from any competently constructed and operated 1P machine (regardless whether "consumer-grade," "gaming," "server" or "workstation" or any other marketing term is applied to describe the intended end use or performance level):
In other words (and ignoring the potential unavailability of required financial resources and differences in interface technologies), if you can build a 1P machine, you can build a 2P, 4P, or 8P machine.
In this case, the 2P Opteron can be built for roughly the same price as the 1P Core i7-2600K, so as long as the determinant is capital investment dollars, the Opteron is a wiser choice *even* when building a machine intended for mainstream or gaming consumers. When server-level reliability is required, the Opteron easily wins: that's its "home-court advantage."
There isn't a similar case to be made for the Xeon: it's not junk, but the Opteron dominates the market in terms of performance per dollar and (IMHO) the Xeon offers no appreciable advantage for the sort of work you've described.
Best wishes for your build!
ERDTdiver :
Should've been more specific. I have no specific processors in mind, just the basic differences between the two, what is one better at than the other. I'll be using them for a workstation/server set-up. I'd like to do some heavy web programming while also using the computer as a server.